This invention relates to the preparation of perfluoroalkyl-alkyl sulfonic acid compounds and more specifically to their preparation by oxidizing the appropriate perfluoroalkyl-alkyl thiocyanate.
The perfluoroalkyl-alkyl sulfonic acid compounds of this invention are useful as surface active agents and as intermediates in the preparation of water and oil repellency agents.
U.S. Pat. No. 3,810,939 discloses a process for preparing segmented fluorocarbon sulfonic acids and related compounds by reacting a perfluoroalkyl-alkyl halide, a perfluoroalkyl olefin or a perfluoroalkyl substituted aromatic hydrocarbon with selected sulfonation reagents including alkali metal sulfites, alkali metal bisulfites, sulfuric acid, sulfur dioxide, sulfuryl chloride and chlorosulfonic acid. Derivatives of the fluorocarbon sulfonic acids including acid anhydrides, metal salts, sulfonyl halides, and sulfonamides are disclosed.
U.S. Pat. No. 3,825,577 discloses a method of preparing perfluoroalkyl-alkyl sulfonic acid compounds by oxidizing a perfluoroalkyl-alkyl thiocyanate with chlorine or bromine to form a perfluoroalkyl-alkyl sulfonyl halide; thereafter, this compound is neutralized with a base to form compounds having the following formula: EQU C.sub.n F.sub.2n+1 (CH.sub.2).sub.b SO.sub.3 M,
wherein
n=1 to 20, PA1 b=2 to 20, and PA1 M=a metal of Groups IA, IIA, IB, IIB, VIII, NH.sub.4, aluminum or lead radical. PA1 n=1 to 20, and PA1 b=2 to 20 PA1 R=an alkyl, aralkyl, cycloalkyl, aryl, or heterocyclic group, and PA1 n=1 or 2, PA1 n=1 to 20, PA1 b=2 to 20, and PA1 M=H or NH.sub.4. PA1 n=1 to 20, PA1 b =2 to 20, and PA1 Y=Cl, Br or I, PA1 n=1 to 20, and PA1 b=2 to 20. PA1 n=4 and even numbers to 20 with an average of 8 PA1 b=2.
This patent discloses that the perfluoroalkyl-alkyl sulfonic acid compounds can also be formed by reacting a perfluoroalkyl-alkyl halide with a metal sulfite to form compounds having the same formula shown above.